Long, tailored skirts are probably okay in a professional office setting, but flowing skirts tend to also be flowery or floaty or gauzy, and those styles don't work well in professional offices.
Long skirts shouldn't come below the mid-shin, and if they're tailored and belted, the style makes sense, especially worn with low heeled pumps. Some professional offices have an unstated dress code; for women it may be skirts and jackets with pumps, all in solid and serious colors. If you want to be taken seriously at your office, it's better to blend in sartorially and stand out in the excellence of your work. Think of following the dress code as protective coloration.
